The present invention generally relates to spindle motor mounting structures and disk units having the same, and more particularly to a spindle motor mounting structure which is suited for reducing the thickness of the structure and a disk unit which has such a spindle motor mounting structure.
FIG.1 shows a cross section of an example of a spindle motor part of a conventional disk unit. In FIG. 1, a spindle shaft 1 forms a rotor 4 of a spindle motor 12 together with a disk shaped rotor case 3 and magnets 2. The spindle shaft 1 is fit into the rotor case 3, and the magnets 2 are arranged on the lower surface of the rotor case 3. A stator 5 of the spindle motor 12 is formed by a bearing 7 which supports the spindle shaft 1, a support member 8 which rotatably supports the rotor 4 in an axial direction, and coils 9 which are located at positions confronting the magnets 2, and these elements of the stator 5 are provided on a substrate 6.
In this spindle motor 12 in which the rotor 4 is rotatably supported on the stator 5, the entire structure is provided on the substrate 6. In addition, the substrate 6 is fixed to a frame 11 which forms a main body of a disk unit 10 by screws 15 which is screwed in from the back surface of the substrate 6.
If a large external shock is applied to the spindle motor 12 having the above described construction, the spindle shaft 1 may slip out of the bearing 7. If this should happen, the rotor 4 will disengage from the stator 5. For this reason, in the conventional disk unit 10, a flange part 3a is provided on the outer periphery of the rotor case 3, and a washer 13 is fixed to the frame 11 so as to partially overlap the flange part 3a for an appropriate range in the plan view. The washer 13 is fixed to an upper surface of the frame 11 by screws 14 located at a plurality of positions. As a result, even if the rotor 4 should move upwardly in FIG. 1, that is, in a direction disengaging from the stator 5, the flange part 3a will hit the washer 13 and the washer 13 will prevent the rotor 4 from disengaging from the stator 5.
But according to the conventional disk unit 10, the washer 13 and the screws 14 are provided on the upper surface 11a of the frame 11 and therefore project upwardly from the upper surface 11a. If a height of this structure including the washer 13 and the screws 14 from the bottom of the substrate 6 is denoted by H1, a height position of a disk loading surface 3b on which a disk cartridge (not shown) is loaded must be set higher than the height H1. Otherwise, the disk cartridge will hit the screw 14 before reaching the disk loading surface 3b and the loading of the disk cartridge will become difficult. Therefore, in the conventional disk unit 10, the disk loading surface 3b must be set to a height greater than or equal to the height H1 of the head of the screw 14, and there is a problem in that the thickness of the spindle motor mounting structure and thus the thickness of the disk unit 10 cannot be further reduced.